* Do not update appId if it is not null
* Prefer linear transformations to side-effect-based changes
This leaves us open to repeat emits due to updates, but distinct until changed stops those.
Tracker improvements are due to passed in observables with replay causing immediate emits when `expectingEmission`s. This converts to a cold observable that only emits when the tracked observable does _after_ subscribing.
* Prefer while
* PR review
* Improve state documentation
* Add namespace for application id
* Spec out behavior of app id service
* Use state providers for app ids
* Migrate app Id
* Add reactive interface
